To wear the winner's distinctive yellow jersey when this year's Tour de France ends in Paris on July 27, cyclists must make every second count throughout the race's 21 stages and 2,208 miles (3,554 kilometers). A bad day biking through the Alps can push a rider off the leader's list and deep into the pack, which makes access to the latest high-tech cycling equipment crucial.

"There is a mad dash to be the most technically advanced," says Scott Daubert, road bike manager for Trek Bicycle Corporation in Waterloo, Wisc., which supplied Lance Armstrong with bicycles during his historic seven consecutive Tour de France victories. "It doesn't matter if you are talking about the bike, the frame, fork, wheel, helmet on the rider or the clothes they are wearing. There's a lot of research, time and money going into making the fastest products you can legally ride."

Before the start of each of the 21 stages racers will select a bike matched to the specific road conditions and type of racing they will face that day, whether it is a time trial (which pit riders against the clock rather than their fellow racers), a mountain climb or stretch of relatively flat road. It is rare that a rider will change bikes once he begins a stage.

A bicycle frame holds everything together, and today's elite-level racers use those constructed from carbon fiber, a material lighter than aluminum and stronger than steel. "For road bikes, the biggest challenge in bike design is the weight-to-stiffness ratio," Daubert says. A lighter bike is more efficient and takes less energy to pedal down the road or up a hill. When a bike gets too light, however, the rider loses power and control over the cycle as he or she pushes the pedals. "The game is to lose the weight and remain stiff," he says.

Other bike design experts agree. "The use of carbon has allowed us to dramatically save weight and make exceptionally stiff frames," says Nicolas Sims, a spokesman for Specialized Bicycle Components in Morgan Hill, Calif. "If it comes down to a sprint finish in a road race, that person will want a really stiff frame so they get good power delivery."

Felt Racing, LLC, in Irvine, Calif., is providing a U.S. team (sponsored by Garmin International, Chipotle Mexican Grill and H30) with different frame options, each specifically designed for time trials, mountain climbs, sprints or long road stages to determine which will perform best in the variety of conditions encountered during the Tour, which begins Saturday. The team is one of two American teams that will compete in this year's race against 18 other European teams.

Scheduled for the fourth and 20th stages of the route, time trials are all about speed. Since the winner of the Tour is the rider with the lowest time needed to finish all 21 stages, the time trial stages allow the fastest riders to extend their overall lead or narrow the gap held by a competitor higher in the standings.

Specifically designed for speed and efficiency, time-trial bicycles allow riders to adopt an aerodynamic body position, and their frames are designed to slice through the air with minimum resistance. "Specialized time-trial bicycles designed to be extremely aerodynamic and equipped with disc wheels and aerodynamic handlebars, along with custom-designed skin suits and helmets, significantly improve the aerodynamics of our riders," says Allen Lim, physiologist for the Garmin–Chipolte–H30 team.

During the energy-sapping, steep up-mountain stages, riders will use the lightest frames possible. A climbing frame uses different geometry than either road or time-trial bikes to create a bike well-suited to negotiate twists and turns.

Garmin–Chipotle–H30 riders will use a sleek new aero road frame on flat-road stretches that is a hybrid between the time-trial bicycles and climbing bicycles. The hybrid design gives the racer a more comfortable ride over a long road course. With some stages as long as 144 miles (232 kilometers) the racers often change the position of their hands on the handlebars and their riding posture to stay comfortable and efficient.

"We create frames that will cut through the air faster than a standard or traditional round-tube bicycle frame," says Bill Duehring, Felt's president. "We calculate that, in a five-hour race, an athlete can pick up five minutes by the end of the race going the exactly same speed on the aero bike as on a standard bike. That's a huge advantage over someone riding a bike with a round or traditional frame."

Technology advances have also led to performance-enhancing improvements in shifting gears. Riders in the past changed gears by moving a lever attached to a cable that shifted the chain to a different position on the rear wheel hub. But that system, known as a friction system, required frequent adjustments to work efficiently. In 1985 Irvine, Calif.–based Shimano American Corporation introduced so-called index shifting, which gave riders more precise control.

"With index shifting, you move a little lever on the brakes and it shifts crisply," says Chester Kyle, adjunct professor of engineering at California State University, Long Beach. Kyle was in charge of Project '96, an initiative of the U.S.'s governing body for bicycle racing, USA Cycling, to improve bicycle performance before the 1996 summer Olympics in Atlanta, Ga. "As you are climbing, you can shift when you are under load much easier. People tend to shift more often and stay in their comfort zone as far as power output goes." Any bicyclist knows how challenging it can be to change gears while pedaling up a steep incline.

The final stage of the 1989 Tour de France provides the most dramatic example of how advanced technology has assisted a Tour de France rider. At the start of the 15.2-mile (24.5-kilometer) time trial, American Greg LeMond trailed France's Laurent Fignon by 58 seconds, a lead that should have been large enough to protect Fignon's first-place position.

Looking for any possible edge, LeMond used an aerodynamic frame from Trek Bicycles equipped with a new form of handlebars called "aero" bars. Used in limited applications in the U.S. before the Tour, aero bars keep the rider in the most aerodynamic position comfortably. LeMond also wore a tapered helmet and wraparound sunglasses. By the halfway point, he had closed the gap and moved 24 seconds ahead of Fignon. Fignon, foregoing the then-exotic aero bars for a traditional racing bicycle setup, quickly fell behind LeMond's startlingly fast pace. After three weeks and 2,025 miles (3,259 kilometers), LeMond won his second Tour by just eight seconds, the closest margin in the race's history.

So who will win this year's contest? No doubt the bicyclist with the best combo of strength, grit, determination—and bike design. Riders "are looking for every advantage," Duehring says. "If we can build them bicycles that allow them to go faster, that's a huge advantage for them in a race like the Tour de France."